1. Field of the Invention
The present invention provides a projection apparatus, and more particularly, to a projection apparatus for providing multiple viewing angle images.
2. Descriptions of the Related Art
To obtain more vivid and realistic images, corresponding displaying technologies have been developed in succession over recent years to satisfy the viewers' demands. In contrast to early-stage flat panel displays which mainly focus on the improvement of the resolution and colors, the three-dimensional (3D) display apparatuses that have appeared over recent years aim to provide the viewers with a vivid stereoscopic displaying effect.
The stereoscopic displaying effect is achieved primarily by feeding different viewing angle images of an object to the left and the right eyes respectively. According to the vision characteristics of human eyes, when the left and the right eyes receive two images with the same image contents but different parallaxes simultaneously, a 3D image of the object with a sense of level and depth will be perceived by the viewer.
In practice, 3D images are generally viewed either by using glasses or with the naked eye; technical developments over recent years have focused on the latter. Furthermore, when being viewed with the naked eye, the images could be viewed in a time multiplex mode or a spatial multiplex mode. Generally, spatial multiplex mode uses large panel display (LCD or plasma display) that is covered with a directional screen (lenticular type or barrier type.) The multiple pixels on the large panel display are guided by the directional screen to different partitioned zones at an observing plane. From any one of the observing positions, only one of multiple pixels on the panel can be observed.
FIG. 1 is a schematic view of a conventional projection-type stereoscopic display apparatus 1 adopting the time multiplex mode. As shown, the stereoscopic display apparatus comprises a plurality of strip-like light sources 11 disposed adjacent to each other, a Fresnel lens 12 and a liquid crystal display (LCD) panel 13. The strip-like light sources 11 each provide a light beam to the Fresnel lens 12 time-sequentially. The light beam is imaged by the Fresnel lens 12 onto the corresponding viewing zone.
FIG. 2 is a schematic view of another conventional projection-type stereoscopic display apparatus 2 adopting the time multiplex mode. As shown, the display apparatus 2 comprises a light source 21, a polarizer 23, a rotary polygonal mirror 25, a panel 27 and a plurality of optical components 29. The light source 21 generates a light beam that is polarized by the polarizer 23 and then reflected by the rotary polygonal mirror 25 onto the panel 27 for imaging, which produces a scanning-like effect. Then, the optical components 29 project the images of different viewing angles to different viewing zones according to a time sequence. More specifically, the light source 21 generates a first view angle image, a second view angle image, a third view angle image and a fourth view angle image on adjacent viewing zones of the panel 27 in different time sequences. However, this projection-type stereoscopic display apparatus requires the use of a rotary polygonal mirror 25 to realize the above said results. In addition, the rotary polygonal mirror 25 mostly functions in a mechanical way, so considerable noises are produced due to friction. Moreover, with the increasing demand for improved resolution, more viewing angles shall be provided, and thereby, the rotation speed of the rotary polygonal mirror 25 must be increased, which makes the aforesaid shortcoming more prominent.
Therefore, there are still shortcomings and problems to be overcome either in the spatial multiplex mode or the time multiplex mode. Accordingly, it is highly desirable in the art to provide a stereoscopic display apparatus with advantages such as a higher light utilization factor, no mechanical operating elements, low costs, simplified optical configurations and a high resolution without the above said shortcomings and problems.